/**
 * User: alesj
 * Date: 2004.11.15
 * Time: 13:03:00
 */

package com.generalynx.ecos.utils;

import java.io.Serializable;

public final class HashCode
        implements Serializable, Cloneable, Comparable {

    /**
     * Hashcode for a 'null' value.
     */
    private static final int NULL_HASHCODE = 0;

    /**
     * Hashcode for a 'true' boolean
     */
    private static final int TRUE_HASHCODE = 1231; // completely arbitrary

    /**
     * Hashcode for a 'false' boolean
     */
    private static final int FALSE_HASHCODE = 1237; // completely arbitrary

    /**
     * The hash-code value.
     */
    private int value;

    /**
     * Construct a new <tt>HashCode</tt> using the given <tt>int</tt> as the
     * base value.
     *
     * @param value <tt>int</tt> to use as the base value.
     */
    public HashCode(final int value) {
        this.value = value;
    }

    /**
     * Construct a new <tt>HashCode</tt>.
     */
    public HashCode() {
        this(0);
    }

    /**
     * Add the hash-code of the given value.
     *
     * @param b Value to get hash-code from.
     * @return <i>This</i> <tt>HashCode</tt>.
     */
    public HashCode add(final boolean b) {
        value ^= generate(b);
        return this;
    }

    /**
     * Add the hash-code of the given value.
     *
     * @param n Value to get hash-code from.
     * @return <i>This</i> <tt>HashCode</tt>.
     */
    public HashCode add(final byte n) {
        value ^= n;
        return this;
    }

    /**
     * Add the hash-code of the given value.
     *
     * @param n Value to get hash-code from.
     * @return <i>This</i> <tt>HashCode</tt>.
     */
    public HashCode add(final char n) {
        value ^= n;
        return this;
    }

    /**
     * Add the hash-code of the given value.
     *
     * @param n Value to get hash-code from.
     * @return <i>This</i> <tt>HashCode</tt>.
     */
    public HashCode add(final short n) {
        value ^= n;
        return this;
    }

    /**
     * Add the hash-code of the given value.
     *
     * @param n Value to get hash-code from.
     * @return <i>This</i> <tt>HashCode</tt>.
     */
    public HashCode add(final int n) {
        value ^= n;
        return this;
    }

    /**
     * Add the hash-code of the given value.
     *
     * @param n Value to get hash-code from.
     * @return <i>This</i> <tt>HashCode</tt>.
     */
    public HashCode add(final long n) {
        value ^= generate(n);
        return this;
    }

    /**
     * Add the hash-code of the given value.
     *
     * @param f Value to get hash-code from.
     * @return <i>This</i> <tt>HashCode</tt>.
     */
    public HashCode add(final float f) {
        value ^= generate(f);
        return this;
    }

    /**
     * Add the hash-code of the given value.
     *
     * @param f Value to get hash-code from.
     * @return <i>This</i> <tt>HashCode</tt>.
     */
    public HashCode add(final double f) {
        value ^= generate(f);
        return this;
    }

    /**
     * Add the hash-code of the given object.
     *
     * @param obj Value to get hash-code from.
     * @return <i>This</i> <tt>HashCode</tt>.
     */
    public HashCode add(final Object obj) {
        value ^= generate(obj);
        return this;
    }

    /**
     * Get the hash-code.
     *
     * @return Hash-code.
     */
    public int hashCode() {
        return (int)value;
    }

    /**
     * Compares this object with the specified <tt>int</tt> for order.
     *
     * @param other Value to compare with.
     * @return A negative integer, zero, or a positive integer as
     *         this object is less than, equal to, or greater than
     *         the specified object.
     */
    public int compareTo(final int other) {
        return (value < other) ? -1 : (value == other) ? 0 : 1;
    }

    /**
     * Compares this object with the specified object for order.
     *
     * @param obj Value to compare with.
     * @return A negative integer, zero, or a positive integer as
     *         this object is less than, equal to, or greater than
     *         the specified object.
     * @throws ClassCastException Object is not a <tt>HashCode</tt>.
     */
    public int compareTo(final Object obj) throws ClassCastException {
        HashCode hashCode = (HashCode)obj;
        return compareTo(hashCode.value);
    }

    /**
     * Test the equality of this <tt>HashCode</tt> and another object.
     *
     * @param obj Object to test equality with.
     * @return True if object is equal.
     */
    public boolean equals(final Object obj) {
        if (obj == this)
            return true;

        if (obj != null && obj.getClass() == getClass()) {
            return value == ((HashCode)obj).value;
        }

        return false;
    }

    /**
     * Return a string representation of this <tt>HashCode</tt>.
     *
     * @return A string representation of this <tt>HashCode</tt>.
     */
    public String toString() {
        return String.valueOf(value);
    }

    /**
     * Return a cloned copy of this <tt>HashCode</tt>.
     *
     * @return Cloned <tt>HashCode</tt>.
     */
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            throw new InternalError();
        }
    }

    /////////////////////////////////////////////////////////////////////////
    //                           Generation Methods                        //
    /////////////////////////////////////////////////////////////////////////

    /**
     * Generate a hash code for a boolean value.
     *
     * @param value Boolean value to generate hash code from.
     * @return Hash code.
     */
    public static int generate(final boolean value) {
        return value ? TRUE_HASHCODE : FALSE_HASHCODE;
    }

    /**
     * Generate a hash code for a long value.
     *
     * @param value Long value to generate hash code from.
     * @return Hash code.
     */
    public static int generate(final long value) {
        return (int)(value ^ (value >> 32));
    }

    /**
     * Generate a hash code for a double value.
     *
     * @param value Double value to generate hash code from.
     * @return Hash code.
     */
    public static int generate(final double value) {
        return generate(Double.doubleToLongBits(value));
    }

    /**
     * Generate a hash code for a float value.
     *
     * @param value Float value to generate hash code from.
     * @return Hash code.
     */
    public static int generate(final float value) {
        return Float.floatToIntBits(value);
    }

    /**
     * Generate a hash code for a byte array.
     *
     * @param bytes An array of bytes to generate a hash code from.
     * @return Hash code.
     */
    public static int generate(final byte[] bytes) {
        int hashcode = 0;

        for (int i = 0; i < bytes.length; i++) {
            hashcode <<= 1;
            hashcode ^= bytes[i];
        }

        return hashcode;
    }

    /**
     * Generate a hash code for an object array.
     * <p/>
     * <p>Does not handle nested primitive array elements.
     *
     * @param array Array to generate hashcode for.
     * @param deep  True to traverse elements which are arrays to
     *              determine the elements hash code.
     * @return Hash code.
     */
    public static int generate(final Object array[], final boolean deep) {
        int hashcode = 0;

        for (int i = 0; i < array.length; i++) {
            if (deep && (array[i] instanceof Object[])) {
                hashcode ^= generate((Object[])array[i], true);
            } else {
                hashcode ^= array[i].hashCode();
            }
        }

        return hashcode;
    }

    /**
     * Generate a shallow hash code for an object array.
     *
     * @param array Array to generate hashcode for.
     * @return Hash code.
     */
    public static int generate(final Object array[]) {
        return generate(array, false);
    }

    /**
     * Generate a hash code for an object.
     *
     * @param obj Object to generate hashcode for.
     * @return Hash code.
     */
    public static int generate(final Object obj) {
        if (obj != null) {
            return obj.hashCode();
        }

        return NULL_HASHCODE;
    }
}
